On Thu, May 16, 2019 at 07:44:20PM +0530, srikanth wrote: > Hello, > > On power9 host, performing memory hotunplug from ppc64le guest results in > kernel oops. > > Kernel used : https://github.com/torvalds/linux/tree/v5.1 built using > ppc64le_defconfig for host and ppc64le_guest_defconfig for guest. > > Recreation steps: > > 1. Boot a guest with below mem configuration: > <maxMemory slots='32' unit='KiB'>33554432</maxMemory> > <memory unit='KiB'>8388608</memory> > <currentMemory unit='KiB'>4194304</currentMemory> > <cpu> > <numa> > <cell id='0' cpus='0-31' memory='8388608' unit='KiB'/> > </numa> > </cpu> > > 2. From host hotplug 8G memory -> verify memory hotadded succesfully -> now > reboot guest -> once guest comes back try to unplug 8G memory > > mem.xml used: > <memory model='dimm'> > <target> > <size unit='GiB'>8</size> > <node>0</node> > </target> > </memory> > > Memory attach and detach commands used: > virsh attach-device vm1 ./mem.xml --live > virsh detach-device vm1 ./mem.xml --live > > Trace seen inside guest after unplug, guest just hangs there forever: > > [ 21.962986] kernel BUG at arch/powerpc/mm/pgtable-frag.c:113! > [ 21.963064] Oops: Exception in kernel mode, sig: 5 [#1] > [ 21.963090] LE PAGE_SIZE=64K MMU=Radix MMU=Hash SMP NR_CPUS=2048 NUMA > pSeries > [ 21.963131] Modules linked in: xt_tcpudp iptable_filter squashfs fuse > vmx_crypto ib_iser rdma_cm iw_cm ib_cm ib_core libiscsi scsi_transport_iscsi > ip_tables x_tables autofs4 btrfs zstd_decompress zstd_compress lzo_compress > raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx > xor raid6_pq multipath crc32c_vpmsum > [ 21.963281] CPU: 11 PID: 316 Comm: kworker/u64:5 Kdump: loaded Not > tainted 5.1.0-dirty #2 > [ 21.963323] Workqueue: pseries hotplug workque pseries_hp_work_fn > [ 21.963355] NIP: c000000000079e18 LR: c000000000c79308 CTR: > 0000000000008000 > [ 21.963392] REGS: c0000003f88034f0 TRAP: 0700 Not tainted (5.1.0-dirty) > [ 21.963422] MSR: 800000000282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: > 28002884 XER: 20040000 > [ 21.963470] CFAR: c000000000c79304 IRQMASK: 0 > [ 21.963470] GPR00: c000000000c79308 c0000003f8803780 c000000001521000 > 0000000000fff8c0 > [ 21.963470] GPR04: 0000000000000001 00000000ffe30005 0000000000000005 > 0000000000000020 > [ 21.963470] GPR08: 0000000000000000 0000000000000001 c00a000000fff8e0 > c0000000016d21a0 > [ 21.963470] GPR12: c0000000016e7b90 c000000007ff2700 c00a000000a00000 > c0000003ffe30100 > [ 21.963470] GPR16: c0000003ffe30000 c0000000014aa4de c00a0000009f0000 > c0000000016d21b0 > [ 21.963470] GPR20: c0000000014de588 0000000000000001 c0000000016d21b8 > c00a000000a00000 > [ 21.963470] GPR24: 0000000000000000 ffffffffffffffff c00a000000a00000 > c0000003ffe96000 > [ 21.963470] GPR28: c00a000000a00000 c00a000000a00000 c0000003fffec000 > c00a000000fff8c0 > [ 21.963802] NIP [c000000000079e18] pte_fragment_free+0x48/0xd0 > [ 21.963838] LR [c000000000c79308] remove_pagetable+0x49c/0x5b4 > [ 21.963873] Call Trace: > [ 21.963890] [c0000003f8803780] [c0000003ffe997f0] 0xc0000003ffe997f0 > (unreliable) > [ 21.963933] [c0000003f88037b0] [0000000000000000] (null) > [ 21.963969] [c0000003f88038c0] [c00000000006f038] > vmemmap_free+0x218/0x2e0 > [ 21.964006] [c0000003f8803940] [c00000000036f100] > sparse_remove_one_section+0xd0/0x138 > [ 21.964050] [c0000003f8803980] [c000000000383a50] > __remove_pages+0x410/0x560 > [ 21.964093] [c0000003f8803a90] [c000000000c784d8] > arch_remove_memory+0x68/0xdc > [ 21.964136] [c0000003f8803ad0] [c000000000385d74] > __remove_memory+0xc4/0x110 > [ 21.964180] [c0000003f8803b10] [c0000000000d44e4] > dlpar_remove_lmb+0x94/0x140 > [ 21.964223] [c0000003f8803b50] [c0000000000d52b4] > dlpar_memory+0x464/0xd00 > [ 21.964259] [c0000003f8803be0] [c0000000000cd5c0] > handle_dlpar_errorlog+0xc0/0x190 > [ 21.964303] [c0000003f8803c50] [c0000000000cd6bc] > pseries_hp_work_fn+0x2c/0x60 > [ 21.964346] [c0000003f8803c80] [c00000000013a4a0] > process_one_work+0x2b0/0x5a0 > [ 21.964388] [c0000003f8803d10] [c00000000013a818] > worker_thread+0x88/0x610 > [ 21.964434] [c0000003f8803db0] [c000000000143884] kthread+0x1a4/0x1b0 > [ 21.964468] [c0000003f8803e20] [c00000000000bdc4] > ret_from_kernel_thread+0x5c/0x78 > [ 21.964506] Instruction dump: > [ 21.964527] fbe1fff8 f821ffd1 78638502 78633664 ebe90000 7fff1a14 > 395f0020 813f0020 > [ 21.964569] 7d2907b4 7d2900d0 79290fe0 69290001 <0b090000> 7c0004ac > 7d205028 3129ffff > [ 21.964613] ---[ end trace aaa571aa1636fee6 ]--- > [ 21.966349] > [ 21.966383] Sending IPI to other CPUs > [ 21.978335] IPI complete > [ 21.981354] kexec: Starting switchover sequence. > I'm in purgatory git bisect points to commit 4231aba000f5a4583dd9f67057aadb68c3eca99d Author: Nicholas Piggin <npiggin@xxxxxxxxx> Date: Fri Jul 27 21:48:17 2018 +1000 powerpc/64s: Fix page table fragment refcount race vs speculative references The page table fragment allocator uses the main page refcount racily with respect to speculative references. A customer observed a BUG due to page table page refcount underflow in the fragment allocator. This can be caused by the fragment allocator set_page_count stomping on a speculative reference, and then the speculative failure handler decrements the new reference, and the underflow eventually pops when the page tables are freed. Fix this by using a dedicated field in the struct page for the page table fragment allocator. Fixes: 5c1f6ee9a31c ("powerpc: Reduce PTE table memory wastage") Cc: stable@xxxxxxxxxxxxxxx # v3.10+ Regards, Bharata.
